##SVG <radialGradient> <radialGradient>元素必须嵌套在<defs>中

###示例1 径向渐变,从 white 到 blue

<svg height="150" width="500">
  <defs>
    <radialGradient id="grad1" cx="50%" cy="50%" r="50%" fx="50%" fy="50%">
      <stop offset="0%" style="stop-color:rgb(255,255,255);
      stop-opacity:0" />
      <stop offset="100%" style="stop-color:rgb(0,0,255);stop-opacity:1" />
    </radialGradient>
  </defs>
  <ellipse cx="200" cy="70" rx="85" ry="55" fill="url(#grad1)" />
</svg>

代码说明:

  • cx, cy,r 定义的是外层的圆,fx ,fy定义的是内层的圆
  • 渐变可以设置多个颜色,每种颜色都用<stop>指定
  • offset定义了渐变颜色的起止

###示例2

<svg height="150" width="500">
  <defs>
    <radialGradient id="grad2" cx="20%" cy="30%" r="30%" fx="50%" fy="50%">
      <stop offset="0%" style="stop-color:rgb(255,255,255);
      stop-opacity:0" />
      <stop offset="100%" style="stop-color:rgb(0,0,255);stop-opacity:1" />
    </radialGradient>
  </defs>
  <ellipse cx="200" cy="70" rx="85" ry="55" fill="url(#grad2)" />
</svg>